To the Editor: Dr Halsell and colleagues1 reported that myopericarditis occurred at a rate
of 1 per 12 819 primary vaccinees in the US military. Similarly, Drs
Grabenstein and Winkenwerder2 found that
between 0.5% and 3.0% of military vaccine recipients needed short-term sick
leave. Both groups of authors concluded that adverse events occurred at rates
below historical rates, and that a mass vaccination program could be carried
out safely. In both reports, however, vaccine complications were derived using
passive rather than active surveillance. Therefore, the very favorable comparison
of military adverse effect rates to historical rates is misleading.